This invention relates to a process of separating and recovering solids and a clear liquid phase from dispersions wherein the solids are suspended in high-boiling liquids, and in particular, to a process involving separation of the sludge phase from the liquid phase followed by processing of the separated phases.
In conjunction with heterogeneous catalytic processes carried out in the liquid phase and with the collection of dust from tar products formed by the gasification of coal, the dry distillation of coal, the hydrogenation of coal, the extraction of coal and others, it is desired to separate dispersed solids from high-boiling liquids with minimum losses in order to recover the solids and to clarify the liquid of all components which are apt to form sediments.
It is known to accomplish these objects by sedimentation, centrifugation or filtration or by means of hydrocyclones. Where substances having suitable properties are involved, electrostatic separation may be performed or may be combined with one of the preceding processes.
All these processes may be used to produce a more highly concentrated suspension of solids, which is referred to as a sludge phase or filter cake, and a liquid phase having a relatively low solids content. In most cases, the original liquid phase can be removed from the sludge phase by a substitution of the latter by the solvents employed.
In many cases, the substances involved have such properties, e.g., in respect of viscosity, density, etc., that the separation itself can be accomplished only when solvents are added. This is particularly applicable to natural sedimentation by gravity.
In commercial application, the known processes are not satisfactory for a substantially loss-free separation of suspended solids in high-boiling oils, tars and the like without using solvents in considerable amounts and loosing the liquid component.